Recent progress in metallurgy has been concerned with the production of wrought composite metal powder, or mechanically alloyed metal powder, wherein a plurality of starting constituents in the form of powders, at least one of which is a compressively deformable metal, are intimately united together to form a mechanical alloy within individual particles without melting any one or more of the constituents. Such materials have been found to possess improved properties of creep resistance.
Such material, having improved properties of creep resistance, is known as "creep resistant platinum". Specifically, creep resistant platinum, as used herein, refers to a material consisting essentially of platinum and yttria (yttrium oxide) in which the amount of yttria is approximately 0.15 weight percent, that is, 0.65 volume percent.
Benjamin in his U.S. Pat. No. 3,591,362, teaches such a composite metal having at least two metal constituents having a high melting point and up to about 25% by volume of a refractory dispersoid, and having a striated internal structure of mechanically alloyed metal fragments.
Another dispersion strengthened consolidated metal product is taught by Benjamin in his U.S. Pat. No. 3,738,817 wherein he disclosed such a product as being produced from mechanically alloyed metal powder selected from the group consisting of nickel, copper, copper alloys, low alloy steels, monaging steels, zinc-base metals; the columbium-base, tantalum-base, molybdenum-base and tungsten-base refractory metals and the platinum metals and gold-base metals, characterized by a uniform dispersion of about 0.05 to 25 volume per cent of a refractory compound dispersoid in both the longitudinal and transverse direction such that the consolidated metal product contains less than 10 volume percent of segregated regions exceeding three microns in minimum dimensions.
Further, Benjamin in his U.S. Pat. No. 3,738,817 teaches dispersion strengthened consolidated metal products produced by mechanically alloying metal powder, including platinum-base metals, with a refractory compound dispersoid in both the longitudinal and transverse direction.
Subsequent developments have related to thermomechanical processing of dispersion-strengthened precious metal alloys in which, by a series of mechanical deformation and annealing cycles, a creep resistant structure is obtained. The mechanical deformation involves rolling the alloy to obtain a reduction in area and then annealing the rolled alloy for a defined period at elevated temperatures. Generally, annealing times of about five minutes at about 1050.degree. C., prior to further repetition of the rolling and annealing process, have been found satisfactory in the thermomechanical processing of creep resistant platinum. However, such materials as creep resistant platinum which has been thermomechanically processed in this manner will show a creep extension of about 0.03 inches after subjection for eighty hours to temperatures of about 2800.degree. F. at 2000 psi. Since bushings employed in the manufacture of glass fibers operate at temperatures of about 2100.degree. F., bushings produced from creep resistant platinum which has been thermomechanically processed, because of creep, even under more moderate conditions, tend to have unsatisfactory operating lives.